CVE-2026-66337: Libsoup: libsoup: heap buffer over-read via integer underflow in soup_filter_input_stream_read_until()

mediumCVSS 6.5CVE-2026-66337

CSIRTS triage

vendor: GNOME product: libsoup Memory corruption

What: A heap buffer over-read occurs via integer underflow in the soup_filter_input_stream_read_until function.
Who is affected: All users of libsoup that process untrusted input via the affected function.
Urgency: Medium priority; buffer over-read could leak sensitive data or crash the application.
Action: Update libsoup to a patched version when available.

AI-assisted analysis generated from the source advisory — verify against the original.

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Details

Source: Microsoft Security Response Center (INTL · vendor-psirt · site)
Severity: medium — CVSS 6.5
Published: 2026-08-06
Exploitation: Not in CISA KEV at last sync

Original advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-66337

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-663370.23% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 14% of all EPSS-scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-66337	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

mediumCVE-2026-66337: A flaw was found in libsoup. An unsigned integer underflow in the soup_filter_input_stream_rea…nvd

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